The subject matter disclosed herein relates generally to clamping high voltages and more particularly to clamping voltages across photovoltaic arrays.
A photovoltaic cell converts solar energy into electrical energy which is sent to one or more power converters. Certain challenges are encountered with photovoltaic energy generation that are not present in conventional energy generation systems. Examples include high voltage output during cold start conditions, IV droop characteristics of photovoltaic cells, and relatively low energy density (efficiency) of photovoltaic cells.
At low temperatures (such as below about −10° C., for example) the open circuit voltage of a photovoltaic cell can be high enough that the inverter is damaged during cold start operations. One approach to clamp high open circuit voltage during a cold start includes coupling a break chopper at the input of the inverter terminals and including a resistor. However, this approach involves significant expense because the chopper circuitry and the resistor must be able to operate under high voltages. Another approach includes shutting down the inverter at low temperatures and results in loss of power to the grid.
There is a need for an efficient and cost effective approach to allow starting of photovoltaic modules under cold operating conditions without damage occurring from open circuit voltages.